Electrodes of electrochemical devices such as batteries and fuel cells are composed of active material particles, conductive agents, and a polymer binder. The active material particles are loose, fragile powder that need some support to hold the particles together to form a contiguous structure. The active material particles also need to be cast into a layer onto a current collector. Binder materials are responsible for holding the active material particles within the electrode together to maintain a strong connection between the electrode and the contacts.
It is the binder that enables the active material particles to hold together and to form a layer on the current collectors. Typically, these binders are dissolved in solvents such as water to form a solution or dispersion. The active material particles, conductive agent, and binder are mixed together via various methods to form a homogeneous slurry. This slurry is coated onto the current collector and dried to remove the solvent and then pressed to form a smooth and uniform layer. The stability of the electrodes, especially from swelling and contracting due to movement of ions during charge and discharge, is dependent on the binder.
Conventional binders are insulators, lack any ionic and electrical conductivity, are inert, and make no contribution towards the mass and volumetric capacity, energy density, and power density of the electrochemical devices in which they are used.